This invention relates to the use of assistance signals for improved image resolution in Enhanced Definition Television (EDTV).
Current U.S. television broadcast signals conform with a standard formulated by the National Television System Committee (NTSC), providing for 525 horizontal scan lines, a 4-to-3 screen aspect ratio, and allocation of a bandwidth of 6 megahertz per communications channel. This standard further calls for alternating transmission of the odd-numbered and the even-numbered scan lines.
As compared, e.g., with 35-mm motion-picture images, transmissions based on the NTSC standard produce images with less resolution of detail and a less appealing aspect ratio, and similar observations apply to a different standard for conventional resolution television known as PAL (Phase Alternation Line) in use elsewhere. In view of these shortcomings, and to improve upon current television image quality, there have been proposals for a new standard for so-called high-definition television (HDTV) with greater vertical and horizontal resolution. Practicable proposed systems are incompatible with reception by receivers in current use. As an alternative, systems have been proposed which retain compatibility with current receiver standards and which use an auxiliary, low-bandwidth channel of assistance information to help improve upon the quality of present-day broadcasts. Though sometimes also referred to as HDTV in the literature, such systems are more appropriately referred to as enhanced-definition TV (EDTV), and they may be considered as an interim to the introduction of HDTV.
The following are cited as background in the field of HDTV/EDTV:
U.S. Pat. No. 4,916,525, issued Apr. 10, 1990 to J. E. Drummond discloses a system in which compressed vertical resolution-enhancing image data is transmitted during the vertical flyback interval of an NTSC television signal. An appropriately equipped receiver can decompress the compressed image data and add the expanded lines of data to the normal image data of the NTSC signal in interlinear fashion. In a receiver not so equipped, the added data is simply ignored.
U.S. Pat. No. 4,967,263, issued Oct. 30, 1990 to C. B. Dieterich; U.S. Pat. No. 4,926,244, issued May 15, 1990 to M. A. Isnardi; the paper by M. A. Isnardi et al., "Encoding for Compatibility and Recoverability in the ACTV System", IEEE Transactions on Broadcasting, Vol. BC-33 (1987 ), pp. 116-213; and the paper by S. N. Baron et al., "An Evolutionary Approach to Advanced Television Services: The ACTV (Advanced Compatible Television) System" each discloses a four-component, wide-screen, NTSC-compatible EDTV transmission format in which the first component has the aspect ratio and bandwidth specifications of a standard NTSC signal, and in which the other three components contain new information which is added to the first component in a compatible manner to provide a wider aspect ratio and enhanced definition. The transmitter inserts compressed high-frequency components of the side panel information and horizontal-resolution-enhancing information in a portion of the bandwidth allocated to the chrominance signal, and also provides a vertical-temporal helper signal at baseband to be used by the EDTV receiver for deinterlacing the received signal. The vertical-temporal helper signal consists of the difference between a calculated temporal average value and the actual value of the missing progressive scan line.
U.S. Pat. No. 4,980,764, issued Dec. 25, 1990 to J. M. Henot discloses the use of a helper signal in the transmission of image blocks and superblocks.
B. Girod et al., "Motion-compensating Field Interpolation from Interlaced and Non-interlaced Grids", 2nd International Technical Symposium on Optical and Electro-Optical Applied Science and Engineering: Image Processing Symposium, Cannes, December 1985, pp. 1-8 discloses motion-compensated interpolation of non-interlaced and interlaced grids for minimizing blur and jerkiness.
M. Pecot et al., "Compatible Coding of Television Images, Part 1: Coding Algorithm", Image Communication Journal (Special Issue on HDTV), pp. 1-18 discloses optimization of band splitting and decomposition filters in sub-band coding of high-resolution image information.
G. W. Meeker, "High Definition and High Frame Rate Compatible N.T.S.C Broadcast Television System", IEEE Transactions on Broadcasting, Vol. 34 (1988), pp. 313-322 discloses a wide-screen, high-definition television system which is compatible with the present NTSC system. The transmitter inserts horizontal-resolution-enhancing information in the bandwidth reserved for the chrominance signal and provides within the NTSC bandwidth motion vectors to be used by the receiver for motion compensated deinterlacing for enhancing vertical resolution.
T. Fukinuki et al., "Extended Definition TV Fully Compatible with Existing Standards", IEEE Transactions on Communications, Vol. COM-32 (1984), pp. 948-953 and T. Fukinuki et al., "Extended-Definition TV Fully Compatible with Existing Standards--Proposal and Experimental Results", 1984 Winter TV Conference, pp. 354-367 disclose an EDTV system which is compatible with existing NTSC or PAL standards. Horizontal resolution is improved by the transmitter inserting high-resolution luminance components in unused portions of the bandwidth allocated to the chrominance signal. The high-resolution components are detected at an appropriately equipped receiver by field-to-field processing.
W. F. Schreiber et al., "A Compatible High-Definition Television System Using the Noise-Margin Method of Hiding Enhancement Information", SMPTE Journal, December 1989, pp. 873-879 discloses an NTSC receiver-compatible EDTV system in which digital audio and horizontal-resolution-enhancing information are inserted by the transmitter in excess chrominance bandwidth.